Ultraviolet Index: What You Need to
Know

Source: American Academy of Dermatology

Did you know that overexposure to the sun can cause skin and eye
injury? While some sunlight is necessary, too much is dangerous, causing
sunburn, premature aging of the skin, skin cancer, cataracts, allergies,
and damage to the immune system. Though the average person gets 50% of his
or her lifetime sun by the age of 18, everyone needs to be aware of the
dangers of exposure to sunlight.

The ill effects of sunlight are caused by ultraviolet (UV) radiation.
These invisible rays from the sun come in two types, called UVA and UVB,
both of which cause sun-related skin damage.

What Is the UV Index?

The Ultraviolet (UV) Index, developed in 1994 by the National Weather
Service (NWS) and the US Environmental Protection Agency (EPA), helps
Americans plan outdoor activities to avoid overexposure to UV radiation
and thereby lower their risk of adverse health effects. EPA and NWS report
the Index as a prediction of the UV intensity at noon, though the actual
UV level rises and falls as the day progresses.

Previously the UV Index was reported on a scale of 0 to 10+, with 0
representing “Minimal” and 10+ representing “Very High.” The new global
scale (see below) now uses a scale of 1 (representing “Low”) to 11 and
higher (representing “Extreme”), a new color scheme, revised exposure
categories, and different breakpoints between exposure categories. (A UV
Index of “0” is still possible, but there is no corresponding health
message because there either is no UV at that level or the amount is
trivially small.)

Index Number

Exposure Level

< 2

Low

3–5

Moderate

6–7

High

8–10

Very High

11+

Extreme

Always take precautions against overexposure, and take special care
whenever the UV Index is 5 and above.

How Much Sun Am I Getting?

Though the amount of UV radiation to which you are exposed varies with
the time of day, season, latitude, and altitude, it can also be increased
depending on your immediate environment. Clouds actually provide little
protection from UV rays, and clouds, water, white sand, concrete, and snow
all reflect UV rays and increase exposure. Of course, exposure to the
midday sun or for long periods of time is most damaging.

What Role Does Ozone-Layer Depletion
Play?

The ozone layer shields the earth from the sun's harmful UV rays. Over
the past ten years, scientists worldwide have recorded decreasing levels
of ozone in the atmosphere. Less ozone means that more UV radiation
reaches earth, increasing the danger of sun damage. The cause of the ozone
depletion is under debate, but scientists agree that future levels of
ozone will depend upon a combination of natural and man-made factors,
including the phase-out of chlorofluorocarbons and other ozone-depleting
chemicals.

Effects of Sun

Sunburn. Overexposure to the sun can happen in just a
few hours. A bad reaction includes tenderness, pain, swelling, and
blistering, and may include fever, chills, and nausea. While there is no
cure for sunburn, wet compresses, cool tub baths, and soothing lotions may
help. If you have a bad burn, see your dermatologist.

Tanning. Some people think that a tan means good
health and looks. Dermatologists know that a tan does not prevent
sun damage, it is sun damage. Tanning occurs when the UV rays
penetrate the skin and injure the pigment cells. The effects are
cumulative, and with every burn, the skin becomes more damaged.

Premature wrinkling. People who work or lay in the sun
without sufficient protection get sagging cheeks and deep wrinkles that
may make them look much older. The sun can also cause unsightly red,
yellow, gray, or brown spots and scaly growths that may develop into skin
cancer.

Skin cancer. Skin cancer is caused by too much sun,
both long-term exposure and bad sunburns. More than 90 percent of all skin
cancers occur on parts of the body exposed to the sun. The face, neck,
ears, forearms, and hands are the most common places for skin cancer to
develop.

The three main types of skin cancer are basal cell, squamous cell, and
melanoma.

Basal cell carcinoma usually appears as a small, shiny, fleshy
nodule on the exposed parts of the body. It grows slowly and rarely
spreads to other parts of the body; but it can severely damage skin around
and below it. When diagnosed and treated early, it has a high cure
rate.

Squamous cell carcinoma typically develops on the face, ears,
lips, and mouth, beginning as a red scaly patch. It also has a high cure
rate when detected and treated early but left untreated, squamous cell
carcinoma can spread to other areas of the body and can be fatal.

Melanoma is the most dangerous form of skin cancer and usually
appears as a dark brown or black lump with irregular edges. Sometimes, it
is multicolored with shades of red, blue, or white. If ignored, melanoma
can spread or metastasize to other areas of the body, which can be
fatal.

Eye damage. The sun can cause cataracts and other eye
damage. Cataracts are one of the leading causes of blindness.

Immune system suppression and disease. Short periods
of sun exposure can damage the human immune system and make the body more
susceptible to infections and cancers. Also, some diseases can become
worse with sun exposure. These include herpes simplex (cold sores),
chicken pox, lupus, and certain genetic problems.

What Are Proper Precautions?

Preventing skin cancer and eye damage. Skin cancer is
increasing faster than any other form of cancer, with over 1 million new
cases predicted to occur in the U.S. this year.

Listen to the UV Index reports.

Minimize sun exposure at midday (10:00 a.m. to 4:00 p.m.)

Avoid sunlamps, tanning beds and tanning parlors.

Apply a broad-spectrum sunscreen with Sun Protection Factor-15 or
higher and reapply every 2 hours.

Wear protective, tightly-woven clothing, a broad-brimmed hat and
sunglasses. Children who will not wear sunglasses should wear a hat with
a wide brim.

Protect children by keeping them indoors between 10:00 a.m. and 4:00
p.m., and by applying sunscreen to children older than 6 months.
Children under the age of 6 months should be kept out of the sun.

Need More Information?

For more information on the UV Index, please call the EPA
Stratospheric Ozone Hotline, 800-296-1996, or the National Weather
Service, 301-713-0622.